Annie has always been a treat lover.
Until recently she has always been free fed dry Royal Canin and in the evening shared a 3 oz. can of wet food with Henry.
Over time she has lowered her food intake and demanded more treats.
With Henry's passing (just 5 days ago) she seems to want only treats and will howl until her command is answered. I know this is not a good situation but I'm at a loss to get her back on track.
Any ideas?

There has been such a change in the daily routine at your house after sweet Henry passed, it must be due to that. I don't know of any really good advice except, trying to keep the schedule as it was, with of course more play & attention to her instead of treats. I hope after a short while she will be back to her normal self.

Cut out treats all together and see if you can force her back to regular food. It is better to do this before she starves herself to the point that forcing it becomes more dangerous. Then use regular kibble hand fed as the treat. When she demands treats, offer hand fed kibble and take that time for interactive games. (Treats are not a balanced diet and should not become a significant part of the diet.)
I just saw that you said that, although it has gotten worse since Henry died, her intake of food had already been decreasing over time. Did the timing of that entirely corresponded to Henry's illness? Has she lost weight? if the answer to the first question is "no" or the answer to the second question is "yes", she should see the vet in case there is an underlying health issue going on. I know that you're overloaded and grieving right now and the last thing you want is to go back to the vet's office, so the timing *really* sucks, but if something physical (rather than purely behavioral) is going on, it's obviously better to catch it earlier rather than later.
Both of these replies sound reasonable to me. I was actually thinking that you take out the treat, show it to her, and then bury it in some wet food.

Have you already tried that?
I have dry food out on two different levels - one in the kitchen and another small plate in our bedroom, which is primarily where she sleeps at night. She has had this arrangement for almost seven years. The kitchen location seems completely untouched since early yesterday. Bill said that she did eat from the bedroom location early this morning.
As soon as we get up in the morning, her routine is to cry for treats. She usually needs two sets
(approximately 20 pieces) to quiet her. As I said, she used to eat the wet food with Henry (around 4 PM) and then just like a child who insists on dessert, she howls for her treats. I have actually fought with her, saying "no treats until you eat your dinner." This used to work, now no matter what she will not touch the wet food and I give up - haven't had the desire to argue with her.
Sarah - her taste for treats has increased over the last six months to a year. So, it actually has been progressing since before Henry's illness. She has not lost weight - I think if anything she has gained weight. When the vet was here on Tuesday, I brought her to him. He was over-whelmed and told her over and over again how beautiful she was.
Kris - I have not tried burying the treats, but I will certainly do so - hoping this might help.
Jan - I thought of complete treat removal and it may be the only way out of this situation, but trust me - it won't be easy. I think at this point she has a serious treat addiction. Also, her treats are placed on a paper plate (vs the ceramic dry food plate). We have tried placing the dry food on the paper plate, suggesting that it might be a treat but she just turns her nose up and walks away. She then continues to cry until she gets her treats!
As always, my thanks to all. I will try the suggestions and keep you posted. I know that a vet visit is never wasted, and Annie deserves all of the best. XO
Maybe if you smeared the wet food on your hand, fingers ect she would eat it! i read this worked for some on another thread.

That was me it worked for Becky - and it works great. I think Teddy likes the special attention - and maybe Annie would like that too. Try is Cheryl...but I would not take away all her treats - she just lost her best friend - and you can't explain to her you are taking away her treats because it's good for her unfortunately. Try putting her treats and her wet food on the paper plate. I hope something works soon - poor Annie!
Can you find some healthier 'treats'? I recently got a sample of some freeze dried chicken (Stella and Chewy's brand) and Valentino loves it given as a treat.
Just a thought...
So very sorry for the loss of your sweet, beloved Henry! And best wishes for the resolution of this issue with beautiful Annie.